Expression of the Tribolium castaneum (Coleoptera: Tenebrionidae) hsp83 gene and its relation to oogenesis during ovarian maturation

Heat shock proteins (HSP) can protect organisms and cells from thermal damage. In this study, we cloned the full length cDNA encoding the HSP83 protein (the homologue of HSP90) of Tribolium castaneum (red flour beetle). The isolated cDNA contains the full coding sequence, a partial 5' untranslated region of 55 bp and the complete 3' untranslated region. We found the hsp83 gene is located on chromosome 5 of the T. castaneum genome. The predicted HSP83 protein sequence has a high similarity (on average 86.77%) with that of other insect species. The expression of the hsp83 gene in the whole body and in the ovary could be induced with heat stress (40 degrees C for 1 h) in newly hatched (within 3 h post emergence) and mature (10 days post emergence) beetles. Under normal conditions, the hsp83 expression in the ovary is about 3-fold higher than in the whole body at both stages. No significant difference in hsp83 expression was observed between the two ovarian developmental stages regardless if the beetles were treated with heat shock or not. The expression of the HSP83 protein in the whole body could also be induced with heat stress in newly hatched and mature beetles. However, in the ovary, HSP83 was only expressed in the follicle cells of mature beetles and not in newly hatched beetles, regardless if the beetles were treated with heat shock or not. Furthermore, the females were not able to produce mature oocytes after knock-down of the hsp83 expression by injecting dsRNA. These results suggest that the HSP83 protein is involved in protection against heat stress and could be involved in oogenesis during ovarian maturation of T. castaneum.